Refrigerating apparatus with frost free compartment



Aug. 28, 1962 1.. J. MANN ETAL 3,050,956

REFRIGERATING APPARATUS WITH FROST FREE COMPARTMENT Filed July 8, 1960 4Sheets-Sheet 1 2 3 INVENTORS L eonard J. Mann The/r Attorney Aug. 28,1962 1.. J. MANN ETAL REF RIGERATING APPARATUS WITH FROST FREECOMPARTMENT Filed July 8, 1960 4 Sheets-Sheet 2 lllllH l l lllllll IIIHIH w ll I/I'H PHI I I i l H III III: III! L'JJ.

Fig. 3

s mm Nu. m mM W4 0 d r Md m 0 LJ Y M/ Fig. 2

Their Attorney Aug. 28, 1962 L. J. MANN ETAL 3,050,956

REFRIGERATING APPARATUS WITH FROST FREE COMPARTMENT Filed July 8, 1960 4Sheets-Sheet s INVENTORS Leonard 4. Mann BY J /m J. OGonne/l Their A/fomey Aug. 28, 1962 1.. J. MANN ETAL REFRIGERATING APPARATUS WITH FROSTFREE COMPARTMENT Filed July 8, 1960 4 Sheets-Sheet 4 Jill. M 26 L M 2 22 2 O M. n 3 8 5 T I 9 8 2 $3 2 2 (ll 2 9 0 2 7. 2 B 2 2 2 0 0 3 3 0 9 59 2 2 o L A wm mfl i l l ll mw mw am HHHHHH 1 IHIIHIIHH INVENTORSLeonard ,1. Mann Th'r Attorney Fig. 5

3,@5il,956 Patented Aug. 28, 1962 .513 filing REFRIGERATING AIPARATUSWITH FROST FREE COMPARTMENT Leonard J. Mann and John J. OConnell,Dayton, Uhio, assiguors to General Motors Corporation, Detroit, Mich., acorporation of Delaware Filed July 8, 1360, Ser. No. 41,612 5 Claims.(Ul. 62-283) This invention relates to refrigerating apparatus and moreparticularly to household refrigerators with above and below freezingcompartments in which frost will not collect.

Refrigerators that are free of frost are popular. Be-

cause of the high sale price, they are limited to those having largerincomes. This is particularly caused by the fact that these frost freerefrigerators have been built with separate evaporators for eachcompartment. Attempts have been made to cool both compartments with asingle evaporator. However, the rapid accumulation of frost from the airreceived from the above freezing compartment causes the evaporator airspaces to become rapidly clogged with frost so as. to prevent the propercirculation of the air between the compartments and the evaporator. Thisrequires frequent defrosting. Furthermore, because of the relativelylarge accumulation of frost where the circulating air first contacts theevaporator, it is difficult to defrost the evaporator rapidly enough toprevent the below freezing compartment temperature from rising anundesirable amount.

It is an object of this invention to provide an arrangement in which asingle evaporator, although it cools air from both the above and belowfreezing compartments, is shielded from substantially all the moisturecarried by the above freezing compartment air in circulation.

It is another object of this invention to remove most of the moisturefrom the air from the above freezing compartment in the form of frostbefore it contacts the surfaces of the evaporator which cools the air ofboth the above and below freezing compartments.

These and other objects are attained in the two forms shown in thedrawings in which the refrigerator cabinet is provided with separateabove and below freezing compartments; In the one form, air from thebelow freezing compartment is drawn through the heat transfer ductwithin a duct from which air from the above freezing compartment isdrawn. The heat transfer surfaces are maintained at a below freezingtemperature by the cold air from the below freezing compartment. Themoistore-laden air from the above freezing compartment flows through itsoutlet duct in heat transfer relation with the cold heat transfersurfaces and deposits the greater portion of its moisture in the form offrost upon the heat transfer surfaces. After this heat transfer, the airfrom both compartments is drawn through an evaporator maintained atabout F. by a fan which discharges the air back into both the above andbelow freezing compartments. The air to the above freezing compartmentis controlled by a thermostatically controlled valve controlled by thetemperature of the air flowing out of the above freezing compartment.The refrigerating system supplying refrigerant to the evaporator iscontrolled by a thermostat bulb located adjacent the inlet to the belowfreezing compartment.

In the second form, separate air circuits are provided for the below andabove freezing compartments. The air from the below freezing compartmentis drawn through the evaporator maintained at about 0 F. by a fan whichdischarges the air back into the below freezing compartment. The airfrom the above freezing compartment is drawn through a heat transferdevice which is cooled by the cold air discharged from the fan whichcirculates the air from and to the below freezing compartment. This airfrom the above freezing compartment is drawn through the second aircircuit and heat transfer device and returned to the above freezingcompartment. The above freezing compartment air is cooled by the heattransfer device and the moisture in this air is removed in the form offrost on the heat transfer device during the operating periods. In boththe forms, the moisture-laden air is prevented from contacting theevaporator so that the evaporator does not frost rapidly and does notbecome so frosted as to prevent the how of air through it. Any form ofdefrosting means may be provided to separately defrost the evaporatorand the heat transfer device.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein [preferred embodiments of the present invention areclearly shown.

In the drawings:

FIGURE 1 is a front vertical sectional view taken along the line 1-1 ofFIGURE 2 of a two-compartment refrigerator embodying one form of ourinvention;

FIGURE 2 is a transverse vertical sectional view taken along the line2-2 of FIGURE 1;

FIGURE 3 is a fragmentary vertical sectional view taken along the line33 of FIGURE 1;

FIGURE 4 is a front vertical sectional view taken substantially alongthe line 4-4 of FIGURE 5 of a second form of the invention;

FIGURE 5 is a transverse vertical sectional view taken along the line5-5 of FIGURE 4;

FIGURE 6 is a wiring diagram for the form shown in FIGURES l to 3; and

FIGURE 7 is a wiring and control diagram for the form shown in FIGURES 4and 5.

Referring now to FIGURES 1 to 3, there is shown an insulatedrefrigerator cabinet 20 having side walls 22, insulated top wall 24,insulated bottom wall 26 and a horizontal intermediate wall 28 dividingthe cabinet into an upper above freezing compartment 30 and a lowerbelow freezing compartment 32. The below freezing compartment 32 isprovided with an evaporator intake air duct 34 extending out from theupper sides down into the interior of a larger discharge air duct 36located in the same side wall 22 extending downwardly from the lowerside of the above freezing compartment 30. Between the evaporator intakeduct 34 of the below freezing compartment and the discharge duct 36 ofthe above freezing compartment are provided fins or other heat transfersurfaces to provide an extensive surface by which air from the abovefreezing compartment can attain adequate contact and be cooled. The airpassing through the evaporator intake duct 34 is at a temperaturenormally below 5 F. so that it is maintained at a relatively coldtemperature. Since it is of metal, it provides a aoeasee cold surface onwhich moisture from the moisture-laden air discharged from the abovefreezing compartment will collect upon in the form of frost. This driesthe moistore-laden air.

Above [the bottom wall 26 there is provided a primary refrigerantevaporator 33 of the vertical fin and tube type located directly beneaththe false bot-tom wall to of the compartment 32. Preferably, this wallit is in direct contact with the fins of the evaporator 38 to providedirect conduction for freezing water in ice trays 41 and maintainingfrozen foods at a low temperature. This evaporator 33 is located withinan evaporator compartment 46 provided between he false bottom wall 40directly above the insulated bottom wall 26. The vertical fins of theevaporator 33 extend from side to side. On the left side of theevaporator 38, there is provided a centrifugal fan 42 having an inlet 44communicating with the evaporator compartment 45 and having a fan scroll'48 formed in the bottom wall. The fan 42 is driven by an electric motort) extending through the bottom wall 26.

The air from the scroll 48 is discharged through an evaporator dischargeair duct 52 formed in the left side wall 22. Some of this air isdischarged through an opening 54 in the upper left side of the belowfreezing compartment 32, while the remainder is discharged through anevaporator discharge duct 56 in the left side wall of the above freezingcompartment 36. The duct 56 discharges the air through an upperdischarge outlet 58 in the upper side Wall of the above freezingcompartment 30. The discharge through this outlet 58 is controlled by adamper 60 which in turn is controlled by a thermostatic device includingan actuating bellows 62 connected by a capillary tube 64 with athermostat bulb 66 located adjacent the air outlet 68 of the abovefreezing compartment 30.

A conventional refrigerating system is provided including a sealedmotor-con1pressor unit '70, a condenser 72 and a capillary tuberest-rictor 74 located in the machinery compartment 76 operativelyconnected to the evaporator 38. The duct 34 is provided with an electricdefrost heater 78 for melting frost from the outer surfaces of the duct34 and the fins 35 in between the duct 34 and the duct 36. Theevaporator 38 is provided with a separate defrost heater St} located inthe bottom of its fins. The frost water during the energization of thedefrost heaters 78 and 8b is collected by a discharge device or drain 82directly beneath the duct 34 which carries away the defrost water fromboth the duct 34 and the evaporator 38. It is located in a shallow wellbeneath the duct 34.

The evaporator 38 is provided with a defrost limiter thermostat 84 toterminate the defrosting periods. The refrigerating system is normallycont-rolled by a thermostat bulb 86 located adjacent the dischargeopening 54- in the left side wall of the below freezing compartment 32.The outlet opening is designated by the reference character 88 andconnects directly with the duct 34 As shown in FIGURE 6, the motor forthe sealed unit 70 as well as the fan motor 50 has one terminalconnected to the supply conductor 9d. The second terminal of each ofthese motors 70 and 50 is connected in series with the thermostaticswitch contacts 92 controlled according to the temperature of thethermostat bulb 86 which is responsive to the air delivered to the belowfreezing compartment 32. This thermostatic switch 92 is connected inseries with a defrost timer 94 which in turn is connected to the secondsupply conductor 96. An additional conductor 93 connects the conductor90 with the defrost timer 94 to supply current for the timin gmechanism, such as a clock mechanism.

The defnost timer 94 is arranged to periodically disconnect thethermostatic switch 52 from the supply conductor 96 to prevent theoperation of the compressor motor 70 and the fan motor 5%. During thistime, the

timer closes switch contacts which energize the defrost circuit whichincludes a conductor E21 connecting in parallel with the defrost heaters73 and 8t) and a conductor 123 connecting with defrost limiterthermostat and a conductor 125 connecting the limiter thermostat withthe timer. When the limiter thermostat 84 reaches a high enoughtemperature to insure defrosting of the evaporator 33, it operatesthrough an operating connection 127 to return the defrost timer 94 tothe normal refrigerating condition in which the thermostat 92 isconnected through the timer 9% to the conductor as.

Through this arrangement, periodically, refrigeration is stopped and thedefrost heaters 78 and 89 energized for a sufficient period of time tomelt the frost from the evaporator intake duct 34 and the fins 35 aswell as the evaporator 33. This defrost water is collected in the wellbeneath the duct 34 and discharged through the defrost water dischargedevice 82 into the machinery compartment 76. In this form, the humid airfrom the above freezing compartment is dehumidified by the heat transferwith the evaporator intake duct 34 prior to its joining with the coldair issuing from the duct 34. Thus, all the air is at a low relativehumidity prior to its contact with the evaporator 38. This reduces theamount of frost depositing on the evaporator 38 in the flow of air tothe inlet 44 of the fan 42 so that the evaporator will not become soclogged with frost that free air flow is retarded. The reduction in theaccumulation of frost also makes possible rapid and complete defrostingof the evaporator 33 during the defrosting periods.

In FIGURES 4 and 5, there is shown a form in which the cabinet issimilar but slightly different and is designated generally by thereference character 22%. It includes side walls 222, an insulated topwall 224, an insulated bottom wall 226 and a horizontal intermediatewall 228 which separates the upper above freezing compartment 23% fromthe lower below freezing compartment 232. The lower below freezingcompartment 232 has a false bottom wall 246 providing an evaporatorcompartment are between it and the insulated bottom wall 226. Avertically finned evaporator 238 is provided in the evaporatorcompartment 246 with the tops of the fins in contact'with the falsebottom wall 24% to promote freezing of the ice in the ice trays usuallyprovided in this compartment. The below freezing compartment 232 isprovided with an outlet 238 connecting with an evaporator inlet duct 234in turn connecting with one side of the evaporator compartment 246.

The opposite side of the evaporator compartment is provided with the fan242 having an inlet 244 communieating directly with the evaporatorcompartment 246 on the outlet side of the evaporator 23%. The fan 242 isdriven by an electric motor 259 and has a discharge scroll 248discharging into an upwardly extending evaporator outlet or dischargeduct 252 along the left side wall of the evaporator compartment 246.This evaporator outlet duct 252 terminates in a discharge outlet 254 atthe upper portion of the left side of the below freezing compartment232. The evaporator 238 is maintained at about -12 F. by a conventionalrefrigerating system including a sealed motor-compressor unit 270, acondenser 272 and a capillary tube restrictor 274 located in themachinery compartment 276 beneath the bottom insulated wall 226. Thecirculation of the air from the below freezing compartment in heattransfer with the evaporator 238 by the fan 242 keeps the compartment232 at temperatures between 0 and 5 F. insuring good storage conditionsfor frozen foods and rapid freezing of water in any ice trays.

For the purpose of cooling the above freezing compartment 234 the outerside of the evaporator outlet duct 252 is provided with a heat transferwall 253 provided with outwardly extending fins 235. Air flows in asecond air circuit out of the above freezing compartment 230 through twooutlets 266 on the lower left side wall thereof which connect withdownwardly extending ducts 236 forming part of the duct 256 andcontaining the two portions of the fins 235 located on opposite sides ofthe dual spaced dividing walls 251 between which is provided an upwardlyextending duct. This air passes downwardly in the ducts 236 through thefins 235 on the outermost side of the dividing wall 251 to the bottom249 of the duct 256 in the left side wall. This duct 256 encloses thevertical fins 235 and conveys the moisture-laden air from the abovefreezing compartment 230 through the outer ducts 236, through the fins235 where the air is cooled and the moisture deposited in the form offrost. The air then flows beneath the lower edges of the fins 235 andthe dividing walls 251 into the upwardly extending duct portion 257located between the dividing walls 251 and containing a central set ofvertical fins 235. This duct portion 257 extends upwardly to the inletof the centrifugal fan 320 driven by the electric motor 322. The fan 320has its inlet on the motor side and discharges the air upwardly throughthe discharge outlet 324 forming a duct which connects with the outlet326 discharging into the upper left side of the above freezingcompartment 230.

A thermostat ibulb 328 adjacent the outlet 326 controls the operation ofthe fan motor 322 while a thermostat bulb 286 located adjacent theoutlet 254 of the below freezing compartment 232 controls the operationof the sealed motor-compressor unit 220 and the fan 250 as shown in thewiring diagram in FIGURE 7. The evapo- T8201 238 is provided with adefrost heater 280 while the heat transfer surface 253 is provided witha separate defrost heater 278. The control system shown in FIG- URE 7includes a supply conductor 290 connecting with the compressor motor 270and the fan motors 250 and 322. The second terminals of the compressormotor 270 and the fan motor 250 are connected to a snap acting switch292 controlled according to the temperature of its thermostat bulb 286.The second terminal of the fan motor 322 is connected through the snapacting switch 331 and the conductor 333 to a junction connecting withthe second terminal of the switch 292. This junction is connected to oneterminal of the defrost timer 294 having its second terminal connectedto the second supply conductor 296. The defrost timer is suppliedindependently through a conductor 298 from the supply conductor 290 tooperate the clock or other timing device.

According to this arrangement, the compressor motor 270 and the fanmotor 250 will cycle according to the temperature of the thermostat bulb286 to maintain the below freezing compartment 232 at a desiredtemperature. The switch 292 may be set, for example, to close at +2 F.and to open at 10 F. The switch 331 may be set to close at 36 F. and toopen at 32 F. Periodically, the timer 294 will disconnect from thejunction to deenergize [the compressor motor 270 and the fan motors 250and 322 and energize the defrost heaters 278 and 280 through the limiterthermostat 284. This energization will continue until the limiterthermostat 2S4 reaches its tripping point at a temperature sufiicientlyhigh, such as 50 F, to insure defrosting of both the evaporator 238 andthe heat transfer surfaces 253 and the fins 235. When this temperatureis reached, the defrost limiter 284 will return the defrost timer 294 tothe normal condition, thus reenergizing the compressor motor 270 and thefan motors 250 and 322 and at the same time deenergizing the defrostheaters 278 and 280.

This arrangement completely isolates the air of the above freezingcompartment from the evaporator 238 and the air circuit of the belowfreezing compartment 232. By providing separate air circuits, the majorpor-- 6 herein disclosed, constitute preferred forms, it is to beunderstood that other forms might be adopted.

What is claimed is as follows:

1. A refrigerator including insulating means enclosing a below freezingcompartment and an above freezing compartment, means forming anevaporator compartment outside said compartments, an evaporator portionwithin said evaporator compartment, first air duct means having a firstportion extending from said below freezing compartment to saidevaporator compartment and having a second portion extendingfrom saidevaporator compartment to said below freezing compartment, said air ductmeans in said first portion including an air to air heat transfer devicehaving heat transfer wall means normally maintained at below freezingtemperatures by air flow through said first duct means, second air ductmeans having a first portion extending from and carrying air from saidabove freezing compartment first into heat transfer relation with saidheat transfer wall means of said heat transfer device and thereafter tosaid evaporator compartment and having a second portion extending fromsaid evaporator compartment to said above freezing compartment, saidheat transfer wall means being located to keep separated the air fromsaid below and above freezing compartments in said heat transfer device,and means for circulating air simultaneously through said first andsecond duct means into heat transfer relation with said heat transferdevice and thereafter through said evaporator compartment into heattransfer with said evaporator portion.

2. A refrigerator including insulating means enclosing at below freezingcompartment and an above freezing compartment, means forming anevaporator compartment outside said compartments, an evaporator portionwithin said evaporator compartment, means for circulating air from saidbelow and above freezing compartments simultaneously through saidevaporator compartment in heat transfer with said evaporatorportion andin contact with each other and returning the cooled air to said belowand above freezing compartments, means for controlling the circulatingair to maintain the above freezing compartment at temperatures abovefreezing, and air to air heat transfer means having heat transfer Wallmeans located between and separating the colder air leaving the- 3. Arefrigerator including insulated means enclosing a below freezingcompartment and an above freezing compartment, means forming anevaporator compartment outside said compartments, refrigerantevaporating means associated with said evaporator compartment, means forcirculating air from said below and above freezing com-v partmentsthrough said evaporator compartment in heat transfer with saidevaporating means and returning the cooled air to said below and abovefreezing compartments, and means for removing moisture from the aircirculating from said above freezing compartment while it is separatedfrom the below freezing compartment air prior to contacting saidevaporating means.

4. A refrigerator including insulated means enclosing a below freezingcompartment and an above freezing compartment insulated from each other,means forming an evaporator compartment outside said compartments,refrigerant evaporating means associated with said evaporatorcompartment, means for circulating air from said below and abovefreezing compartments through said evaporator compartment inintermixture with each other and in heat transfer with said evaporatingmeans and returning the cooled air to said below and. above freezingcompartments, and means for removing moisture from the air circulatingfrom said above freezing compartment prior to contacting air circulatingfrom said below freezing compartment and prior to its entrance into theevaporator compartment.

5; A refrigerator including insulated means enclosing a below freezingcompartment and an above freezing compartment, means forming anevaporator compartment outside said compartments, refrigerantevaporating means associated with said evaporator compartment, means forcirculating air from said below and above freezing compartments throughsaid evaporator compartment in heat transfer with said evaporating meansand returning the cooled air to said below and above freezingcompartment, and means for substantially cooling the air circulatingfrom said above freezing compartment while it is sepa- :2: rated fromthe below freezing compartment air prior to its circulation in heattransfer with said evaporating means.

References Cited in the file of this patent UNITED STATES PATENTS2,265,634 Cumming Dec. 9, 1941 2,416,354 Shoemaker Feb. 25, 19472,481,616 Richard Sept. 13, 1949 2,546,363 Iaeger Mar. 27, 19512,863,300 Murphy Dec. 9, 1958 2,889,692 McGraw June 9, 1959 2,982,115Wurtz May 2, 1961

